'\" te
.\" Copyright (c) 2002, Sun Microsystems, Inc.  All Rights Reserved
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.TH RBAC 7 "Jul 15, 2003"
.SH NAME
rbac, RBAC \- role-based access control
.SH DESCRIPTION
.sp
.LP
The addition of role-based access control (RBAC) to the Solaris operating
environment gives developers the opportunity to deliver fine-grained security
in new and modified applications. RBAC is an alternative to the all-or-nothing
security model of traditional superuser-based systems. With RBAC, an
administrator can assign privileged functions to specific user accounts (or
special accounts called roles).
.sp
.LP
There are two ways to give applications privileges:
.RS +4
.TP
1.
Administrators can assign special attributes such as setUID to application
binaries (executable files).
.RE
.RS +4
.TP
2.
Administrators can assign special attributes such as setUID to applications
using execution profiles.
.RE
.sp
.LP
Special attribute assignment along with the theory behind RBAC is discussed in
detail in "Role Based Access Control" chapter of the \fISystem Administration
Guide: Security Services\fR. This chapter describes what authorizations are and
how to code for them.
.SS "Authorizations"
.sp
.LP
An authorization is a unique string that represents a user's right to perform
some operation or class of operations. Authorization definitions are stored in
a database called \fBauth_attr\fR(5). For programming authorization checks,
only the authorization name is significant.
.sp
.LP
Some typical values in an \fBauth_attr\fR database are shown below.
.sp
.in +2
.nf
solaris.jobs.:::Cron and At Jobs::help=JobHeader.html
solaris.jobs.grant:::Delegate Cron & At \e
    Administration::help=JobsGrant.html
solaris.jobs.admin:::Manage All Jobs::help=AuthJobsAdmin.html
solaris.jobs.user:::Cron & At User::help=JobsUser.html
.fi
.in -2

.sp
.LP
Authorization name strings ending with the \fBgrant\fR suffix are special
authorizations that give a user the ability to delegate authorizations with the
same prefix and functional area to other users.
.SS "Creating Authorization Checks"
.sp
.LP
To check authorizations, use the \fBchkauthattr\fR(3SECDB) library function,
which verifies whether or not a user has a given authorization. The synopsis
is:
.sp
.in +2
.nf
int chkauthattr(const char *authname, const char *username);
.fi
.in -2

.sp
.LP
The \fBchkauthattr()\fR function checks the \fBpolicy.conf\fR(5),
\fBuser_attr\fR(5), and \fBprof_attr\fR(5) databases in order for a match to
the given authorization.
.sp
.LP
If you are modifying existing code that tests for root UID, you should find the
test in the code and replace it with the \fBchkauthattr()\fR function. A
typical root UID check is shown in the first code segment below. An
authorization check replacing it is shown in the second code segment; it uses
the \fBsolaris.jobs.admin\fR authorization and a variable called
\fBreal_login\fR representing the user.
.LP
\fBExample 1 \fRStandard root check
.sp
.in +2
.nf
ruid = getuid();

if ((eflag || lflag || rflag) && argc == 1) {
        if ((pwp = getpwnam(*argv)) == NULL)
                crabort(INVALIDUSER);

        if (ruid != 0) {
                if (pwp->pw_uid != ruid)
                        crabort(NOTROOT);
                else
                        pp = getuser(ruid);
        } else
                pp = *argv++;
} else {
.fi
.in -2

.LP
\fBExample 2 \fRAuthorization check
.sp
.in +2
.nf
ruid = getuid();
if ((pwp = getpwuid(ruid)) == NULL)
        crabort(INVALIDUSER);

strcpy(real_login, pwp->pw_name);

if ((eflag || lflag || rflag) && argc == 1) {
        if ((pwp = getpwnam(*argv)) == NULL)
                crabort(INVALIDUSER);

        if (!chkauthattr("solaris.jobs.admin", real_login)) {
                if (pwp->pw_uid != ruid)
                        crabort(NOTROOT);
                else
                        pp = getuser(ruid);
        } else
                pp = *argv++;
} else {
.fi
.in -2

.sp
.LP
For new applications, find an appropriate location for the test and use
\fBchkauthattr()\fR as shown above. Typically the authorization check makes an
access decision based on the identity of the calling user to determine if a
privileged action (for example, a system call) should be taken on behalf of
that user.
.sp
.LP
Applications that perform a test to restrict who can perform their
security-relevant functionality are generally \fBsetuid\fR to root. Programs
that were written prior to RBAC and that are only available to the root user
may not have such checks. In most cases, the kernel requires an effective user
\fBID\fR of root to override policy enforcement. Therefore, authorization
checking is most useful in programs that are \fBsetuid\fR to root.
.sp
.LP
For instance, if you want to write a program that allows authorized users to
set the system date, the command must be run with an effective user \fBID\fR of
root. Typically, this means that the file modes for the file would be
\fB-rwsr-xr-x\fR with root ownership.
.sp
.LP
Use caution, though, when making programs \fBsetuid\fR to root. For example,
the effective \fBUID\fR should be set to the real \fBUID\fR as early as
possible in the program's initialization function. The effective \fBUID\fR can
then be set back to root after the authorization check is performed and before
the system call is made. On return from the system call, the effective UID
should be set back to the real \fBUID\fR again to adhere to the principle of
least privilege.
.sp
.LP
Another consideration is that \fBLD_LIBRARY\fR path is ignored for setuid
programs (see SECURITY section in \fBld.so.1\fR(1)) and that shell scripts must
be modified to work properly when the effective and real \fBUID\fRs are
different. For example, the \fB-p\fR flag in Bourne shell is required to avoid
resetting the effective \fBUID\fR back to the real \fBUID\fR.
.sp
.LP
Using an effective \fBUID\fR of root instead of the real \fBUID\fR requires
extra care when writing shell scripts. For example, many shell scripts check to
see if the user is root before executing their functionality. With RBAC, these
shell scripts may be running with the effective \fBUID\fR of root and with a
real \fBUID\fR of a user or role. Thus, the shell script should check
\fBeuid\fR instead of \fBuid\fR. For example,
.sp
.in +2
.nf
WHO=`id | cut -f1 -d" "`
if [ ! "$WHO" = "uid=0(root)" ]
then
       echo "$PROG: ERROR: you must be super-user to run this script."
       exit 1
fi
.fi
.in -2

.sp
.LP
should be changed to
.sp
.in +2
.nf
WHO=`/usr/xpg4/bin/id -n -u`
if [ ! "$WHO" = "root" ]
then
       echo "$PROG: ERROR: you are not authorized to run this script."
       exit 1
fi
.fi
.in -2

.sp
.LP
Authorizations can be explicitly checked in shell scripts by checking the
output of the \fBauths\fR(1) utility. For example,
.sp
.in +2
.nf
for auth in `auths | tr , " "` NOTFOUND
do
    [ "$auth" = "solaris.date" ] && break       # authorization found
done

if [ "$auth" != "solaris.date" ]
then
    echo >&2 "$PROG: ERROR: you are not authorized to set the date"
    exit 1
fi
.fi
.in -2

.SH SEE ALSO
.sp
.LP
.BR ld.so.1 (1),
.BR chkauthattr (3SECDB),
.BR auth_attr (5),
.BR policy.conf (5),
.BR prof_attr (5),
.BR user_attr (5)
.sp
.LP
\fISystem Administration Guide: Security Services\fR
